Spoiler to Python Challenge (help!!!)

[Ian Vincent]

Damn this is annoying me.

I have a webpage with a BZ2 compressed text embedded in it looking like:

'BZh91AY&SYA\xaf\x82\r\x00\x00\x01\x01\x80\x02\xc0\x02\x00 \x00!\x9ah3M
\x07<]\xc9\x14\xe1BA\x06\xbe\x084'

Now, if I simply copy and paste this into Python and decompress it - it
works a treat.

However, I want to read the file containing this data, extract the data
and decompress it and this for some reason does not work.

I am doing the following (excuse the probably very long handed way of
doing it):

file = urllib.urlopen(url, proxies=proxies)
line = file.readlines()
file.close()
line = line[20:]
line = line[:-1]
user = line[0]
password = line[1]
user = user[5:]
user = user[:-2]
user = str(user)
password = password[5:]
password = password[:-2]

This gives me a user string of:

BZh91AY&SYA\xaf\x82\r\x00\x00\x01\x01\x80\x02\xc0\x02\x00 \x00!\x9ah3M
\x07<]\xc9\x14\xe1BA\x06\xbe\x084

But if I put this into the decompression function, I get a error of
'IOError: invalid data stream'.

I know it is the escape characters but how do I get these to be correctly
converted into a string compatible with bz2.decompress()?

 

[Terry Hancock]

I have a webpage with a BZ2 compressed text embedded in it looking like:

'BZh91AY&SYA\xaf\x82\r\x00\x00\x01\x01\x80\x02\xc0\x02\x00 \x00!\x9ah3M
\x07<]\xc9\x14\xe1BA\x06\xbe\x084'

Now, if I simply copy and paste this into Python and decompress it - it
works a treat.

However, I want to read the file containing this data, extract the data
and decompress it and this for some reason does not work.
[...]
This gives me a user string of:

BZh91AY&SYA\xaf\x82\r\x00\x00\x01\x01\x80\x02\xc0\x02\x00 \x00!\x9ah3M
\x07<]\xc9\x14\xe1BA\x06\xbe\x084

But if I put this into the decompression function, I get a error of
'IOError: invalid data stream'.

I know it is the escape characters but how do I get these to be correctly
converted into a string compatible with bz2.decompress()?

Took me a long time to figure out what you meant. ;-)

So the string actually contains the backslashes, not the escaped characters.

This works:
'huge'

(which I take it is what your sample data encoded -- though I can't help
but notice it is actually much shorter than the "compressed" version. ;-)).

This may have some security issues, though, since it evaluates essentially
any expression given for user. I'd be interested to know if someone
knows a more secure way.

Cheers,
Terry

 

[Terry Reedy]

line = line[20:]
line = line[:-1]

please, line = line[20:-1], etc, is easier to read and understand ;-)

tjr

 

[Ian Vincent]

please, line = line[20:-1], etc, is easier to read and understand ;-)

Thanks, i'll put that in.

 

[Ian Vincent]

Took me a long time to figure out what you meant. ;-)

So the string actually contains the backslashes, not the escaped
characters.

This works:

'huge'

Unfortunately, it doesn't. Get the same error.

 

[Terry Hancock]

'huge'

Actually, it doesn't -- I sent you the wrong version of the email.

THIS works (and is what actually produced the output above).

Sorry about that. I was trying the other as an alternative,
but in fact, it doesn't work. So ignore that.

Cheers,
Terry

 

[Ian Vincent]

Sorry about that. I was trying the other as an alternative,
but in fact, it doesn't work. So ignore that.

Excellent! Thanks.

 

[Christos Georgiou]

This works:


This may have some security issues, though, since it evaluates essentially
any expression given for user. I'd be interested to know if someone
knows a more secure way.

given

a = "a tab\\x09between"

this is more secure than eval:

b= a.decode("string_escape")